Up to now, cell frames, bipolar plates, collector plates, and/or other solid constructive parts of fuel cells, in particular of low-temperature fuel cells such as the PEM fuel cell, have been known that are manufactured from graphite or other carbonaceous materials. The thickness of the plates ranges from at least 2 to 2.5 mm, due to the gas and liquid distribution structure, and, despite the low density of the plate material the plate cause the cells to have a comparatively high weight and large volume.
In EP 0 629 015 Al, the following alloys or metals are disclosed as materials for bipolar or collector plates: aluminum, titanium or alloys thereof, zirconium, niobium, tantalum, or alloys of these five elements. In addition, it is there disclosed that these elements can be passivated by protective electrically insulating oxides, and that, alternatively to the above-named metals, the plates can also be made of more corrosion-resistant materials such as graphite, high-alloy stainless steel, or nickel-chromium alloys. However, more precise statements concerning the composition of well-suited alloys of these metals have not been known up to now.
For mass production, the carbonaceous materials are too heavy and too expensive in the manufacture of cell frames, current collectors and/or bipolar plates, etc. In turn, the metals have an excessively high susceptibility to corrosion, and, due to their passivation by oxide layer formation, have excessively high losses during current transport inside the fuel cell.
Therefore there is a need for a fuel cell suitable for mass production, in which the collector plates and/or cell frames and/or other constructive parts of the fuel cell are made of a material that
is economical and corrosion-resistant (even in direct contact with the acid membrane electrolytes), and PA1 is easily transformable (good deep-drawing quality), and PA1 has a low contact resistance, and finally PA1 has a low thickness and, above all, a low weight in the processing into plates, despite the gas and liquid distribution structure.
The subject matter of the invention is a fuel cell that comprises a membrane electrode unit, two current collectors and,or a cell frame and/or a bipolar plate, whereby the material of at least one of the solid constructive parts is made of an Fe-based material selected from the alloys with the following compositions:
C content: 0-0.06 weight % Si content: 0-2 weight % Cr content: 8.25-46.5 weight % Mo content: 1.25-14.0 weight % Ni content: 2.25-40.5 weight % Cu content: 0-4.0 weight % Mn content: 0-13 weight % N content: 0.02-1 weight % Nb content: 0-0.5 weight % P content: 0-0.09 weight % S content: 0-0.06 weight % Fe content: remainder to 100 weight %
As an iron-based material, Fe is in principle the main component of the inventively used alloy, whereby the designation main component cannot be defined by percent indications, but rather is regarded relative to the other components.
Moreover, the subject matter of the present invention is the use of an iron-based alloy with one of the above-named compositions in the construction of a fuel cell.